Various types of breathing or respiratory devices have been constructed or proposed to provide pulmonary therapy to a medical patient or other individual by assisting his breathing in a manner which improves his lung capacity. Preferably, the breathing devices provide for terminating the exhalation period at a predetermined positive expiratory end or residual lung pressure, for example, between three centimeters of water and twelve centimeters of water. Such a device which provides for positive expiratory end pressure or residual lung pressure is commonly referred to as a "Peep" device.
One form of Peep device is disclosed in U.S. Pat. No. 3,710,780 wherein air is exhaled through a tube submerged within a body of water which produces a predetermined back-up pressure or head. Another form of Peep device incorporates a valve having a magnetically actuated valve member and wherein an adjustable permanent magnet controls the pressure at which the valve opens. A further type of portable Peep device resembles a smoking pipe and incorporates a spherical valve member or ball which is urged by gravity against an annular valve seat.
In view of the usual physical weakness of an individual requiring pulmonary therapy, it has been found highly desirable for a Peep device to provide for exhalation at a substantially constant predetermined Peep pressure and to offer a minimum or preselected resistance to exhalation at the Peep pressure so that minimum effort is required by the individual during exhalation. It is also important for the device to assure a positive closing or cut-off of the exhalation air flow immediately when the exhalation pressure drops below the predetermined Peep pressure to assure that the residual pressure is maintained within the lungs until at least the start of inhalation. If the device has even a small leak, the residual lung pressure quickly dissipates through the Peep device.
It has also been found desirable for the Peep device to provide for conveniently and precisely selecting between different predetermined Peep or residual lung pressures so that the device may be adjusted or regulated according to the conditions of each individual user. In addition, the device should not be dependent upon gravity for operation or require a volume of liquid so that the device may be conveniently used by an individual at any place and in any position. It is apparent after analyzing the construction and operation of the previously known Peep devices that none of the devices provide for all of the above mentioned desirable features.